When I was 13 my geography teacher, “BO” Brown, had legendary jungle-strength armpits. Maybe it’s mean to bring it up now, but then it was reckless of him to write “Joseph is enthusiastic but misses the point”

on my report, so I feel vindicated.

I wonder why he always smelled so bad, and why no other adult told him. And what about the kids? I don’t remember one child mentioning it. There’s an outside chance he had hyperhidrosis, the unfortunate condition that makes you stink no matter what you do. But that’s unlikely, and anyway, Mr Brown wasn’t the only one. A heady bouquet of sweat, fags and stale coffee wafted your way whenever certain teachers drew close. Either they didn’t know about it or they didn’t care.

Teachers aren’t the only culprits. Last year, I went to Normandy on my first residential school trip as a teacher. Apart from sleep deprivation and weapon confiscations, everything was going well until my colleagues decided I should discuss personal hygiene with two boys who’d smelt foul from the moment we boarded the coach.

You’d be forgiven for thinking this was a straightforward chat. But I never managed it. In the preceding months I’d dealt with snot, sick and other squeamish nasties, but when it came to body odour I bottled it.

I’m not the only one who finds this subject awkward. “When someone smells bad, other people find it embarrassing to talk about, so they make excuses and don’t do it,” says Dr Susan Marchant-Haycox, a psychologist from the American Intercontinental University in London who specialises in communication. “Mentioning smell feels like you’re making a personal assault on somebody, like telling them they’re ugly. Because of this, people often try to pass the buck and get someone else to mention the issue.”

It seems that discussing other people’s hygiene is a touchy subject - for me, my colleagues and everybody else. But is it acceptable for teachers to ignore it?

The science of smell is mysterious - almost magical - and scientists readily admit that they don’t really understand it. The perfume and flavour industries (smell is closely related to taste) often work by guessing at combinations until they stumble upon an effective one.

Smells manipulate our behaviour and self-belief. We can associate certain smells with success or failure; being exposed to them will help or hinder our performance. Dr Simon Chu from the University of Central Lancashire has suggested we could harness this phenomenon to help children with emotional and behavioural difficulties, using certain aromas to trigger memories that reinforce positive behaviour.

Smell-related memories are often vivid. Some experts, including Dr Chu, argue that smell memories work differently from others, triggering primitive, “reptilian” responses in the brain. For Dr Chu, the whiff of open drains brings back a moment from his Hong Kong childhood when he was attacked by a giant bee. You probably have a food or flower smell that rekindles an emotion from your own childhood.

Subtle, ambient odours can even generate these emotions before you’ve noticed what’s creeping up your nostrils. While mild odours can have a strong psychological effect, powerful smells such as body odour prompt a dramatic response. Research shows that, in small doses, this smell can be attractive. The age of sweat is a major factor here; new sweat does not smell at all.

Sweat appears in an odourless state but is quickly broken down by bacteria on the skin. Every individual has his or her own smell, and we instinctively use smell to seek out mates. If someone’s natural smell is very different from our own, and if we breed, apparently the children we have with them will be good at fighting illness.

But when the odour grows too strong, it becomes repellent. Glands in the armpits and groin produce sweat with lots of fat molecules, and they produce the nastiest smell when broken down. Young children don’t produce many of these, but around the age of eight this starts to change. By their teens, children are producing almost as many pungent molecules as adults.

Perhaps this is why teenagers are so enthusiastic about deodorant and perfume. Some students smother themselves in them. One afternoon, after a choking entrance from some Year 8 girls, I tried to get to the bottom of this. “Why do you put so much on?” I asked Tara in as teacherly a manner as I could muster.

“We do it because the boys smell, Sir,” she replied, surprised. “What, am I in trouble?”

Her question is significant. Putting on perfume or deodorant is one of the few ways students feel they can express themselves without getting in trouble. Chewing gum, jewellery and make-up may be barred, but you can’t police body scents. Students often use them to show who they’re mates with; they all share the same perfume that day. This doesn’t just apply to girls; many boys take an interest, but often this is the post-sport “shower in a can” method of keeping themselves BO-free, which is, at best, a short-term solution (see panel below).

That’s not to say teenage girls don’t pong from time to time; just ask anyone who’s taught a double lesson in a girls’ school on a hot day. But there is some truth in the old adage: “horses sweat, men perspire, women glow”. On average, teenage boys sweat far more than girls. They have bigger sweat glands and need to release more liquid to regulate their body temperature.

Stress is another factor. My NQT year was peppered with tricky lessons, and they always seemed to crop up on the days when I’d opted for a sweat-revealing grey shirt. Halfway through the lesson I’d move to take my jacket off but notice I was having a “Tony Blair” moment, with dark rings surging round my armpits. I’d quickly ease the jacket back on, hope no one had noticed, and sweat it out. Nowadays I steer clear of grey shirts.

Occasional stinky days are an unavoidable hazard for many of us, but round-the-clock BO is a more pressing concern. George Orwell (who was obsessed with smells) argued that it is the most vulnerable members of society who smell bad. This definitely applies in schools. It is one thing thoughtlessly to pick up a dirty shirt and wear it, but when students regularly wear clothes that are caked in days-old sweat, this is not simply an issue of teenage lethargy; there is a strong chance that the child is being neglected. As teachers and teaching assistants, we have a duty of care, and this includes personal hygiene.

“If a child isn’t clean, and smells, then that child’s basic needs aren’t being met,” argues David Coulter, the National Society for the Prevention of Cruelty to Children’s policy adviser on education and employment.

Neglect is defined as “a persistent failure to meet a child’s basic physical or psychological needs”, so consistently dirty clothes may be the first sign of it.

Coulter is worried that teachers receive inadequate training in child protection (one to three hours). It’s easy to see how teachers, especially NQTs, could miss or ignore smell-related signs of neglect. “Not getting involved is not an option,” Coulter insists, arguing that taboos around talking about personal hygiene can damage the children who need us most.

At least I feel more experienced on the subject now. Thinking back to “BO”

Brown, it’s hardly surprising that none of us plucked up the courage to tell our teacher he smelled. But these days it would be better for everyone if we learned how to broach the subject.

Access DfES guidance, Safeguarding Children In Education, at www.dfes.org.uk. Joe Curtis (pictured) teaches English at St Paul’s RC school, London borough of Greenwich. Email comments on classroom smells to joecurtisemail@yahoo.com